This invention relates to a device for oxidizing certain exhaust emissions from diesel engines, for vehicles or stationary applications.
It is well known that diesel engines emit noxious exhaust by-products which are not only a nuisance to the public, but a health hazard as well. Therefore, complete public acceptance of diesel engines will not occur until the noxious constituents of their exhausts have been substantially cleaned up. The U.S. E.P.A. has established, by regulations, levels for such emissions which are at present considered tolerable, but insofar as the applicant is aware, no one has been able to design a system which can meet them satisfactorily.
This invention relates to a device containing a filter means for connection to a diesel engine to process the exhaust. The device collects soot, and certain particulate emissions, and disposes of them during engine operation either (1) by what is herein called "natural regeneration" when the temperature of the filter is high enough, or else (2) by what is herein called "forced regeneration" when the filter, due to insufficiently high temperatures, becomes loaded with particulates to the pointwhere it either may not function properly or else otherwise interfere with the vehicle's operation. The latter type of regeneration is initiated by an associated electronic control unit which receives signals from various sensing devices associated with the engine and/or with the collecting and oxidizing device itself. In both types of regeneration processes, soot which has been accumulated in the device is burned out and the by-product, carbon dioxide mainly, is disposed of into the atmosphere. The device may be endowed with particular catalyst formulation which also oxidizes hydrocarbons and carbon monoxide thereby substantially reducing, if not essentially entirely eliminating, diesel odor.
The invention comprises a number of features which individually and collectively contribute to its ability to clean up diesel engine exhaust. These features relate to: (1) the sensing of when the device has become loaded to the point where forced regeneration should be initiated; (2) the manner of by-passing the collection and oxidizing zone during forced regeneration; (3) control of the forced regeneration process; (4) the manner in which forced regeneration is performed; (5) the manner in which exhaust is forced to flow through the device; (6) the configuration of the filter; and (7) the overall organization of the device.
The foregoing features are disclosed in a first embodiment of the invention. Also disclosed herein is a second embodiment which contains further features beneficial to soot collection efficiency. They are: 1) a pre-converter for the control of hydrocarbon (HC), carbon monoxide (CO), and volatile portion of the particulates; and 2) an electrostatic augmented arrangement in which the particulates are pre-charged across a corona discharge medium ahead of the filter element.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode presently contemplated in carrying out the invention.